1. Field of the Invention
The present invention relates to a neutral position determination method for a speed change gear shaft for an electrically operated speed change gear wherein gear shifting and connection or disconnection of a clutch are performed electrically. More particularly, the present invention relates to a neutral position determination method for a speed change gear shaft for an electrically operated speed change gear which performs predetermined speed change control based on a rocking direction and a rocking angle of the speed change gear shaft which is rocked by a drive motor.
2. Description of Related Art
While a conventional speed change gear performs gear shifting by operation of a clutch pedal (or a clutch lever) and a shift change lever, an electrically operated speed change gear which performs gear shifting making use of motor power is disclosed in the official gazette of Japanese Patent Laid-Open No. Hei-5-39865. Furthermore, it is possible to perform connection or disconnection of a clutch simultaneously using a motor.
In this instance, the speed change gear shaft is rotated by the drive motor, and connection or disconnection of the clutch is controlled in association with the speed change gear shaft. Furthermore, a sleeve is driven on a main shaft through a shift drum and a shift fork which operates in association with the speed change gear shaft so that the sleeve is engaged with a predetermined gear to establish a shift stage.
The operation timing must be determined based on a rotational angle of the speed change gear shaft. Therefore, when connection or disconnection of the clutch and rotation of the shift drum, etc. are performed in association with the speed change gear shaft, the rotational angle of the speed change gear shaft must be detected accurately.
If it is intended to represent the rotational position of the speed change gear shaft with a relative rotational angle from the middle position of the rocking motion of the speed change gear shaft, i.e., a neutral position, then mounting of an angle sensor or connection of an angle sensor and the speed change gear shaft or the like must be performed accurately so that an output voltage of the angle sensor when the speed change gear shaft is in a neutral position may indicate a predetermined value.
Furthermore, even if the angle sensor, etc. can be mounted accurately, if the sensitivity of the angle sensor is varied by a secular deterioration, then the rotational position of the speed change gear cannot be detected accurately.